Pain, both acute and chronic, afflicts millions of people around the world.
Pain can be categorized in different ways, but one of the most common is nociceptive versus neuropathic pain.
Nociceptive pain is the result of activity in signaling pathways caused by actual tissue damage or potentially tissue-damaging stimuli. Examples of nociceptive pain include postoperative pain, arthritic pain and pain associated with sports injuries. Nociceptive pain is usually acute and develops in response to a specific situation. It tends to disappear when the affected body part heals.
The body contains specialized nerve cells called nociceptors that detect harmful stimuli or things that can injure the body, such as extreme heat or cold, pressure, crushing and chemicals. These warning signals are then transmitted along the nervous system to the brain, resulting in nociceptive pain. This happens very quickly in real time, as when people quickly remove their hands if they touch a hot oven or stop bearing weight on an injured ankle.
Neuropathic pain is chronic pain that is initiated by dysfunction or damage to the nervous system. Chronic pain is a disability that affects every aspect of the patient’s life, which includes the ability of the individual to work and engage in social and leisure activities. Neuropathic pain affects a total of approximately 7–8 percent of the adult population. People with some conditions, such as diabetes and HIV, are affected
to a greater extent where approximately 25% and 35% respectively experience neuropathic pain. Peripheral neuropathic pain results from various types of damage to the nerve fibers, such as toxic, traumatic, metabolic, infectious or compressional injuries. Common symptoms are painful tingling or itching that can be described as a stabbing or burning pain, including a sensation of getting an electric shock. Patients may also experience allodynia (pain caused by a stimulus that usually does not cause pain) or hyperalgesia (increased pain from a stimulus that normally provokes pain). Three common conditions of neuropathic pain are painful peripheral neuropathy caused by conditions such as diabetes, painful posttherpetic neuralgia (shingles), and neuropathic pain induced by chemotherapy.
A 2012 study from the National Institute of Health’s National Center for Complementary and Integrative Health shows that nearly 50 million American adults experience chronic or severe pain, and according to the American Academy of Pain Medicine, more Americans suffer from pain than diabetes, heart disease and cancer combined. The data from Europe show similar results and health and socioeconomic costs are estimated at 3-10% of gross domestic product in Europe.
The neuropathic pain market is characterized by high unmet medical need in all indications and in all major markets, where only half of patients respond to existing treatments. The patient population is expected to continue to grow, due to factors such as an aging population and increased incidence of type 2 diabetes, as well as cancer requiring chemotherapy. The global market for neuropathic pain was valued at USD 5 billion in 2015 and is expected to grow to USD 8 billion by 2024.
There is currently a major medical need for several different severe pain conditions. For example, only about 50% of patients with neuropathic pain respond to existing treatments. Opiates are generally not recommended as first-line treatment because of the risk of abuse, overdose and secondary injuries.
The advantages of topical or local therapies include lower systemic drug exposure, fewer side effects and fewer drug interactions. Moreover, unlike systemic therapies, titration with locally targeted therapies are not required, either.